1. Technical Field
The present invention relates in general to thermal assisted recording (TAR) applications and, in particular, to an improved system, method and apparatus for fabricating a c-aperture or E-antenna plasmonic near field source for thermal assisted recording applications in hard disk drives.
2. Description of the Related Art
In magnetic recording disk drives, the magnetic material (or media) for the recording layer on the disk is chosen to have sufficient coercivity such that the magnetized data bits are written precisely and retain their magnetization state until written over by new data bits. As the areal data density (the number of bits that can be recorded on a unit surface area of the disk) increases, the magnetic grains that make up the data bits can be so small that they can be demagnetized simply from thermal instability or agitation within the magnetized bit (the so-called “superparamagnetic” effect). To avoid thermal instabilities of the stored magnetization, media with high magneto-crystalline anisotropy (Ku) may be required. However, increasing Ku also increases the short-time switching field, H0, which is the field required to reverse the magnetization direction, which for most magnetic materials is somewhat greater than the coercivity or coercive field measured on much longer time-scales. However, H0 cannot exceed the write field capability of the recording head, which currently is limited to about 15 kOe for perpendicular recording.
Since it is known that the coercivity of the magnetic material of the recording layer is temperature dependent, one proposed solution to the thermal stability problem is thermally-assisted recording (TAR), wherein the magnetic material is heated locally to near or above its Curie temperature during writing to lower the coercivity enough for writing to occur, but where the coercivity/anisotropy is high enough for thermal stability of the recorded bits at the ambient temperature of the disk drive (i.e., the normal operating or “room” temperature). Several TAR approaches have been proposed, primarily for the more conventional longitudinal or horizontal recording, wherein the magnetizations of the recorded bits are oriented generally in-the-plane of the recording layer. However, TAR is also applicable for perpendicular recording, wherein the magnetizations of the recorded bits are oriented generally out-of-the-plane of the recording layer. TAR is also usable with patterned media.
In TAR, it is important to avoid heating data tracks adjacent to the data track where data is to be written because the stray magnetic field from the write head can erase data previously recorded in the adjacent tracks. Also, even in the absence of a magnetic field, heating of adjacent data tracks accelerates the thermal decay over that at ambient temperature and thus data loss may occur. A proposed solution for this adjacent-track interference problem is the use of an optical channel with a small aperture that directs heat from a radiation source, such as a laser, to heat just the data track where data is to be written. This type of TAR disk drive is described in U.S. Pat. No. 5,583,727 and U.S. Pat. No. 6,982,844.
In conventional (non-TAR) disk drives, each read/write head is located on an air-bearing slider that is maintained in close proximity to its associated disk surface as the disks rotate. The films making up the read and write heads are deposited on a wafer containing a large number, e.g., 40,000, of rectangular regions arranged in rows, with each region ultimately becoming an individual slider. After formation of the read and write heads at the wafer level, the wafer is cut into rows and the rows cut into individual sliders. The sliders are then “lapped” in a plane perpendicular to the wafer surface, with this plane becoming the slider's air-bearing surface (ABS). However, for sliders used for TAR disk drives, the only proposed methods for forming an optical channel and/or aperture structure have been to fabricate the optical channel and/or aperture structure on the slider at the row level, i.e., after the wafer has been cut into rows, or at the individual slider level. These are costly and time-consuming methods.
TAR requires small focused light spots that are much smaller than the diffraction limit of the light source. Therefore, regular optical components are not viable for these types of applications. Nanoscale near field plasmonic sources are being considered for use in TAR for fabricating the required optical structures. One of the most promising optical structures is the c-aperture, which can be thought of as an E-antenna. To clarify, the dielectric aperture in this structure looks like the letter “c”, while the metal surrounding that dielectric forms an antenna in the shape of a capital letter “E”. An improved wafer-level process for forming optical channels and aperture structures on air-bearing sliders for use in TAR disk drives would be desirable.